How can I make sure that my products are not also on AliExpress?

If you find good suppliers then your products are probably not going to be on Aliexpress because Aliexpress usually deals with cheaply made products and their customers usually know that they will be getting cheap products. This will cause more work for you in terms of customer support and returns.

​Also, if you do your research (which we highly suggest) you can see what products in your niche are on AliExpress and stay away from the majority of those.